A major problem with large diameter nuts is that they require a very high torque in order to ensure that sufficient bolt tension is created to maintain the tightness of the bolt. This high torque is often very difficult to achieve in a confined aircraft environment, for example. As a result, it is often impossible to prevent the nut from becoming loose without the use of special locking devices, such as an indexed locking device. The indexing device typically includes a series of splines around the circumference of one end of the bolt which are susceptible to corrosion issues.
This problem is not limited to bolts and applies equally to, for example, solid or hollow pivot pins having a threaded end. Such large diameter pins are regularly used to connect the main leg of an aircraft landing gear to a gear rib of an airframe, and as hinge or actuator pins for aircraft flight control surfaces. This problem is not limited to aerospace applications and may be found in virtually any large structure requiring a large diameter nut such as, for example, a crane.